The pacemaker's journey, spanning from the 19th century to current day, showcases remarkable breakthroughs in medicine and engineering. Thanks to computer modelling and simulation, it was possible to tackle a once unsolvable issue: making pacemaker devices compatible with Magnetic Resonance Imaging.
The story of the pacemaker is one of relentless innovation combining medicine and engineering. It is estimated that there are currently more than 3 million people worldwide whose life is sustained by a pacemaker. Such a device generates synchronous electrical signals, which are then propagated to the heart, by wires or so-called leads. Its function is to help maintain a steady heartbeat when the heart’s natural rhythm falters.
The origin of pacemaker technology dates back to the late 19th century when Alexander MacWilliam reported in the British Medical Journal that electrical pulses could sustain a heart rate of 60-70 beats per minute. Then, in the 1950s, the Canadian electrical engineer John Hopps created the first external pacemaker. The device was bulky and posed safety risks due to its reliance on a common wall socket, for power. Additionally, its method of delivering electrical pulse through the skin was quite painful. In 1958, came the first “portable” device, which was developed by the Colombian doctor Alberto Velez Laverde and the electrical engineer Jorge Reynolds Pombo. That “portable” pacemaker weighed an astounding 45 kilograms and was powered by a car battery. Nevertheless, it kept a 70-year-old priest, Gerardo Florez, alive.
The same year in Sweden, Arne Larson became the first person to receive an implantable pacemaker. The operation, performed at the Karolinska Institute by surgeon Ake Senning and inventor Rune Elmqvist, was both groundbreaking and humbling. The initial device was functional for only three hours, and its replacement lasted a mere few days. Despite these setbacks, the patient went on to live 43 more years, albeit requiring 26 device replacements throughout his life. Remarkably, Larsson outlived both the surgeon and the inventor, thanks to the pacemaker.
Larsson passed away in 2001 due to a melanoma. At the time, one critical innovation remained unrealised– allowing patients with a pacemaker to safely undergo Magnetic Resonance Imaging (MRI) scans. MRIs are invaluable for diagnosing disease conditions like tumours and musculoskeletal disorders, which involve soft tissues. But, the strong magnetic fields and radio frequencies generated during MR imaging, pose a significant risk for pacemaker devices and their users. Early research highlighted issues such as the reset of the pacemaker device, rapid pacing, battery drainage, and even over heating of the leads with a risk of damage to the heart muscle and tissues. Therefore, pacemaker patients were advised to avoid MRIs entirely, for decades. This limitation is particularly concerning, as both younger and older populations with pacemakers depend on MRI scans for diagnosing, treating, and monitoring various health conditions.
Solving this challenge was not an easy task, especially the one related to the heating of the pacemaker leads. The number of factors influencing the lead electrode heating were numerous and complex, ranging from patient size, anatomy, body composition, their position in the MRI scanner, all the way to the routing and design of the pacemaker leads. Traditional experimental approaches were insufficient for rigorously testing such a vast number of factors and here is where computer modelling and simulation proved transformative. Engineers used computer models to simulate millions of possible risk scenarios, analysing every possible confounding factor in detail. This approach led to a remarkably straightforward solution: refining the design of the pacemaker lead was sufficient to effectively mitigate the risks posed by heating leads to patients with a pacemaker during the MRI scan.
Today, all major pacemaker manufacturers offer MRI-compatible devices, which are safe to be used in an MRI environment, along with specific guidelines. This breakthrough enabled through in silico medicine technology, today allows millions of patients with pacemakers to access diagnostic imaging and receive comprehensive care.
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